Summary The Heli-Lift International Inc. Bell204B helicopter (registration C-GSHK, serial number2067) was being used to conduct external load operations south of Stony Rapids, Saskatchewan, slinging drill rods between drill sites. Approximately three minutes into the flight, the pilot radioed that his side bubble window door had come open and that he was having difficulty holding the door. The pilot released the sling load and the helicopter was observed climbing in a steep nose-up attitude before momentarily stopping on its tail, then dropping nose down. As the helicopter descended toward the ground, there was an explosion. The helicopter crashed approximately 22nautical miles southwest of Stony Rapids and was destroyed by impact forces and a post-crash fire. The pilot, the sole occupant of the helicopter, was killed. The crash occurred during daylight hours at 1811central standard time. Ce rapport est galement disponible en franais. Other Factual Information Visual meteorological conditions were observed at the time of the occurrence. The 1800 central standard time1 wind at Stony Rapids, 22nm northeast of the accident site, was from the northwest at three knots. The wind at the accident site was estimated to be from the northwest at 13to 17knots. The helicopter underwent a 100-hour inspection on 23July2006, approximately 80flight hours before the accident. A review of the helicopter's technical records indicated that the helicopter was maintained and certified in accordance with existing regulations, all routine and special inspections were complete, and component life limits were adhered to. At the time of the occurrence, there was one defect that had not been rectified, the removal of the heater vent valve, which was minor in nature and did not affect the serviceability of the helicopter. A weight and balance computation for the accident flight indicated that the helicopter was operating within the weight and centre of gravity limitations. The pilot was qualified for the flight in accordance with existing regulations and held a valid commercial pilot licence. His total helicopter flight time was about 10700hours, approximately 600of which were in the Bell204/205 series. He had about 3000 hours of experience in long-line operations. The pilot had completed a Transport Canada pilot proficiency check (PPC) on the Bell205 on 22December2005. As the Bell204/205 series are similar in nature, Transport Canada regards them as sharing a common licensing certification. The PPCwas assessed as a good ride with a very experienced pilot. The pilot underwent a Category 1 Civil Aviation Medical Examination on 29June2006. The pilot was assessed as being fit and in good health. An autopsy was performed after the accident and the post-mortem report indicated that the pilot had quite significant atherosclerosis in his left anterior descending and right coronary arteries with over 70percent stenosis or blockage. It could not be determined whether the blockage had an adverse effect on the pilot in this occurrence. The pilot had no recorded history of cardiovascular disease and his last electrocardiogram (ECG) on 12December2005 was considered normal. The pilot had recently been hired by Heli-Lift International Inc. He took the company initial ground training and visual flight rules (VFR) flight training on 21and 22July2006. The flight training included an initial type-training refresher on the Bell204 system operation and failures, emergency procedures, company procedures, and flight exercises. The ground training included the recognition, prevention and recovery procedures associated with certain abnormal in-flight conditions such as vortex ring state and settling with power. The ground training did not include training about the hazards associated with mast bumping, nor was it a requirement. A survey of operators of medium Bell helicopters found that the hazards associated with excessive blade flapping and mast bumping were not consistently included in recurrent training curricula. The Heli-Lift International Inc. Bell204B helicopter was being used under contract to move two drilling rigs from drill site to drill site as new exploration progressed to the southwest of Stony Rapids. The pilot's first job with the company was the repositioning of the drill rigs from Stony Rapids, which he began on 15September2006. The pilot had arrived in Stony Rapids approximately two weeks before the occurrence and had completed a full move of both drilling rigs during the first week. Late in the afternoon of 24September2006, the smaller of the two rigs was ready to be moved again, and the pilot was called to begin the move. The time between the movements of the drilling rigs was approximately one week. The pilot had not flown the week between the moves and was scheduled to be rotated out of Stony Rapids the day following the occurrence. The helicopter can be flown from either the right or left seat position. The left seat position is equipped with a bubble window door that provides downward visibility to facilitate the positioning of the long-line hook for load pickup. On the day of the accident, the helicopter was parked at the Stony Rapids Airport, across the ramp from the fuelling source. In preparation for flight, the occurrence pilot got into the left seat and hover taxied the helicopter to the fuel tanks, where it was fully loaded with fuel. The long-line was stowed in the rear of the helicopter. A ground worker noticed during the taxi that the bubble door was slightly ajar, indicating that it was closed but not latched. Before take-off after the fuelling, the ground worker again noticed that the door was slightly ajar. He walked over to the helicopter, pushed on the door, and rotated the outside handle to the latched position. The ground worker then waved at the pilot who departed for the 20-minute flight from Stony Rapids to the old drill site, approximately 20nm to the southwest. The helicopter landed at a temporary helipad, out of view of the workers at the old drill site. The pilot installed the long-line and moved the helicopter to the drill site where the first load of drill rods was attached to the long-line hook. The helicopter pilot and ground workers were in radio contact during the hook-up procedure. The helicopter lifted the load and transited from the drill site without difficulty. Approximately three minutes after departure, the pilot radioed an urgent message that he was experiencing a problem with his door. A senior company pilot flying two or three miles away responded. The occurrence pilot asked whether he could release the sling load. The company pilot agreed and asked whether a landing was possible. The occurrence pilot indicated that he could not land because he was holding onto the bubble door with his hand and was afraid of losing the door. There were no more radio transmissions with the helicopter. The helicopter was at an estimated height of 700feet above ground level (agl). The helicopter had no sling load attached and was climbing in a nose-up attitude. The climb got progressively steeper until the helicopter was approximately 1000feetagl. The helicopter paused momentarily in a nose-high attitude, and then dropped nose-down. It descended steeply and, at approximately 500feetagl, an explosion occurred. Smoke and flames trailed behind the helicopter until impact. The main wreckage was located 1.8nm from the old drill site and approximately 0.8nm south of a direct track to the new drill site location. Numerous helicopter components were found spread along a track of about 295T for approximately 1950feet. The length of the wreckage trail and steep impact attitude were consistent with the helicopter suffering an in-flight breakup. A ground fire ensued, which started a forest fire and destroyed much of the main wreckage. The first pieces along the wreckage trail were light items carried within the helicopter. The next items were pieces of main rotor blade skin, pieces of the cockpit and overhead windows, a piece of the instrument panel glare shield, battery cover pieces, the left horizontal stabilizer, and a piece of tail rotor blade. The main rotor assembly and stabilizer bar, the tail rotor assembly, and portions of the 90-degree tail rotor gearbox were approximately 600feet from the main wreckage. The main rotor mast assembly was completely fractured and distorted in a symmetrical oblong nature from contact with the main rotor hub static stops. The wreckage path and damage pattern indicated that the main rotor mast had separated from the helicopter. The bubble door hinges and latching mechanism were in the burnt remains of the main wreckage. The door was still connected by its hinges to the door frame, and the emergency door release handle was in the stowed position. The door latches and door handle were in the unlatched position. Most of the engine and engine accessories were destroyed by fire. A visual examination found the internal turbine wheels to be intact. The hydraulic flight control servos were completely destroyed by fire and could not be examined. An examination of the remaining flight control systems did not reveal any discrepancies. The Bell 204B helicopter's left and right pilot doors are equipped with three roller-type latches, two at the top of the door and one at the rear of the door. When the door is initially closed, the rear roller rolls over a pawl extending out from the rear door frame to hold the door closed. To latch the door, the door handle is rotated 90forward to the closed or latched position. The rotation of the door handle extends the top rollers and latches them behind plates mounted on the upper door frame. The rear roller extends and latches behind the pawl mounted in the rear door frame. A positive lock is accomplished by over-centre linkage. Care has to be taken when closing the door. Over time, these mechanisms often wear due to inherent airframe vibrations and the top rollers may not latch behind the plates if the top of the door is not pulled in tightly when the handle is latched. This often requires two hands to accomplish. If the door is not latched properly, normal airframe vibration may pop the door open in flight. If a cockpit door opens in flight, it will normally stay in the trail position and will virtually be impossible to close until the forward speed is reduced to a near-hovering condition. The doors are also equipped with an armrest to provide support for the pilot's arm during flight. A door-opening incident happened on the occurrence helicopter two to three weeks before the accident. Another company pilot had been performing long-line operations from the left seat position. After completing the lift, the pilot set the helicopter down to load passengers into the rear cabin. The pilot exited the left door, removed the long-line, loaded the passengers, and re-entered through the right door to fly back in the right-seat position. Upon exiting the left bubble door, the pilot closed the door but forgot to latch it. During the return flight, at approximately 60to 80knots airspeed, the left door popped open. Neither the pilot nor any of the passengers in the rear cabin could reach the door. The door opened approximately six to eight inches and stayed in a trailing position. No significant door flapping or controllability problems with the helicopter were noted. The pilot slowed the helicopter and hovered over the ground where he instructed one of the rear cabin passengers to unbuckle, lean forward and close and latch the door. The flight continued on without incident. The Bell204B helicopter is fitted with a teetering, two-bladed main rotor system. The teetering design allows the main rotor blades to flap in order to compensate for asymmetrical lift during flight. Static stops are mounted on either side of the main rotor hub to physically limit the amount of blade flapping when the rotor is not turning. A condition known as mast bumping occurs if the static stops contact the mast due to excessive blade flapping during flight. Excessive blade flapping and mast bumping can occur when there is sudden reduction in g loading on the main rotor. This can happen if the helicopter transitions suddenly from a climb to forward flight. The sudden level-off causes a reduction in g loading and thrust on the rotor blades as the helicopter becomes momentarily weightless. Because the main rotor is not generating thrust, the tail rotor thrust, being above the helicopter's longitudinal axis, causes the helicopter fuselage to roll sharply in the direction of the tail rotor thrust. The main rotor maintains its previous attitude and the clearance between the rotor head and the mast is reduced. The application of lateral cyclic control on the unloaded main rotor has little or no effect to counteract the roll of the fuselage, and acts only to further reduce the clearance between the head and the mast. If the main rotor blades flap too far in one direction in relation to the mast, the static stops on the main rotor hub can strike the rotor mast violently enough to cause separation of the main rotor from the helicopter. To recover from a low-g condition, the best corrective practice is to apply aft cyclic, which loads the rotor system and in turn produces thrust. Once lateral cyclic becomes effective, the helicopter can be rolled to a level attitude.